This application relates to a method and apparatus for abrading contoured surfaces on substrates such as wood substrates.
A very substantial amount of wood surfaces on various pieces of furniture, picture frames, chair rail moldings, crown moldings, floor moldings, doors, etc. have grooves or convex round surfaces that either curve circumferentially as about the edge of a rounded table or extend in a straight line, as on a molding or door. Typically, such contoured surfaces are abraded by hand using pieces of sandpaper or abrasive material embedded in a flat piece of foam. Also, there are so-called "profile" sanders in which a hard pad is contoured to the shape of the substrate surface which is provided with a peelable layer of abrasive, sandpaper and is reciprocated through short strokes by a motor. The operator of this hand-held, profile sanding apparatus pushes it along the contoured substrate surface to sand it. Because the peelable sandpaper layer is attached to a non-rotating, reciprocating, hard layer of rubber of a reciprocating profile sander, the contour of the hard rubber must match very substantially the contour of the surface of the substrate. If the hard rubber contour is slightly larger than, e.g., a contoured groove, then the edge of the sandpaper tends to dig into the edges of the smaller groove. If a concave surface on the hard rubber, profile sander is larger in diameter than the diameter of the convex substrate surface, the abrasive sandpaper rides along one or more spaced straight line surfaces rather than wrapping laterally about and sanding the entire convex surface. These profile sanders that reciprocate are very unforgiving in the sense that it will not conform with the surface and will cause "change of direction" marks on substrates, as well as chattering with higher grit sandpaper.